Set in the eighties inside the dangerous and enigmatic Kowloon Walled City, which was a de jure Chinese enclave within British colonial Hong Kong, Twilight of the Warriors: Walled In follows troubled youth Chan Lok-kwun (Raymond Lam) as he accidentally enters the Walled City, discovers the order amidst its chaos, and learns important life lessons along the way. In the Walled City, he becomes close friends with Shin, Twelfth Master and AV. Under the leadership of Tornado (Louis Koo), they resist against the invasion of villain Mr. Big (Sammo Hung) in a series of fierce battles. Together, they vow to protect the safe haven that is Kowloon Walled City.